This invention relates to novel dyed inorganic composite particles having a specific particle shape and a specific structure, and more particularly, to dyed inorganic composite particles useful as a carrier for preparing an immunological diagnostic reagent by binding an immunologically active substance (an antigen and an antibody) to them, particularly an immunological diagnostic reagent for use in a microtiter method, or as a hydrophilic pigment, and to a process for their production.
Various fine particles of inorganic compounds have previously been known, but most of them are agglomerating gelled particles. The fine particles of inorganic compounds are widely used as various fillers, filling and reinforcing agents, pigments, etc. However, no inorganic compound particles useful as a hydrophilic pigment or as a carrier for use in immunological diagnostic reagents have previously been proposed. For example, in the case of the former, it is difficult to impart hydrophilicity to a pigment only by mixing with inorganic compounds, and neither a suitable composite or a process for its production has been proposed. Gelled particles cannot be used as a carrier for immunological diagnostic reagents, and non-agglomerating and well-dispersible particles have not yet been developed. In particular, various restrictions are imposed on those carriers for immunological diagnostic reagents which are used in the microtiter method because the end point of an agglutination reaction in an immunological reaction should be determined with good accuracy. For example, such carriers are required to be non-agglomerating, have a high specific gravity, and be uniformly colored. However, no fine particles of an inorganic compound having such properties have been provided to date.